He said Turkey would hold captured foreign fighters "for some time. After that we'll send them back to their countries".
Soylu said EU countries including the Netherlands and Britain had stripped some of the fighters of their nationality to prevent Ankara from sending them home.
"They found an easy solution," he said. "They say 'I took his nationality away, it's your problem now'. That's unacceptable in our view, that's totally irresponsible. What do you want me to do with your terrorist?" Turkey last month launched an offensive in north-eastern Syria against a Kurdish militia Turkey has branded "terrorists", but which was at the forefront in the fight against Islamic State with the backing of Western governments.
As part of the offensive, Turkey took Islamic State members into custody who had previously been held by the Kurds.